Wellbores are drilled into the earth for a variety of purposes including tapping into hydrocarbon bearing formations to extract the hydrocarbons for use as fuel, lubricants, chemical production, and other purposes. When a wellbore has been completed, a metal tubular casing may be placed and cemented in the wellbore. Thereafter, a perforation tool assembly may be run into the casing, and one or more perforation guns in the perforation tool assembly may be activated and/or fired to perforate the casing and/or the formation to promote production of hydrocarbons from selected formations. Perforation guns may comprise one or more explosive charges that may be selectively activated, the detonation of the explosive charges desirably piercing the casing and penetrating at least partly into the formation proximate to the wellbore.